How do I acclimate a new fish or invertebrate to my tank?
When: Every time you introduce a new animal — into quarantine, and later into the display
Short answer: Float the sealed bag in your tank until temperatures match, then slowly mix tank water into the bag or a container over time (drip acclimation) instead of dumping the animal straight in. This gives it time to adjust to your tank's salinity, pH, and temperature without shock. Invertebrates are far more sensitive to salinity swings than fish, so never skip the drip step for snails, shrimp, crabs, or anemones.
The details
1. Temperature first. Float the still-sealed bag in the destination tank (quarantine or display) until the water inside the bag matches the tank's temperature. Don't open it yet.
2. Don't stop at float-and-dump. Floating only equalizes temperature. Salinity, pH, and other chemistry are still completely different between bag water and tank water — moving the animal in after only a temperature float can shock it, especially invertebrates.
3. Drip, don't dump. Open the bag, pour the animal and its water into a clean container, and run a thin line — airline tubing with a flow-control valve, or a purpose-made acclimation kit — from the tank into that container so tank water drips in and gradually dilutes the bag water. Aim to roughly triple the starting water volume before the transfer.
4. Match the drip rate to what's in the bag. Invertebrates need it slowest, sensitive fish next, and most other fish and corals can go a little faster (see the numbers table below).
5. Never add the bag water itself to your tank. Discard it. It can carry disease from the store's system, and — counterintuitively — opening a bag and letting its pH rise can convert relatively harmless ammonium into toxic ammonia. Transfer only the animal, never its shipping water.
6. This is a two-time job. You'll drip acclimate once moving the animal into quarantine, and again later moving it from quarantine into the display — see the next card.
The numbers
| Livestock | Drip rate |
|---|---|
| Invertebrates (snails, shrimp, crabs, starfish, anemones) | 1–2 drips/sec |
| Sensitive fish (wrasses, puffers, anthias, gobies) | 2–3 drips/sec |
| Most other fish and corals | 2–4 drips/sec |
| Target dilution | ~3x the bag's original water volume |
Common mistakes
- Float-and-dump — fixes temperature, not chemistry.
- Pouring shipping/bag water into the tank.
- Rushing an invertebrate's acclimation at a fish-speed drip rate.
- Skipping acclimation into quarantine because "it's just a small QT tank."
When to worry
- Normal: the animal looks stressed, pale, or hides right after the move — give it time in a dim, quiet tank.
- Worry: gasping, rolling, or unresponsive behavior during acclimation — stop, re-check your temperature and salinity match, and don't force a rushed transfer.
What's next
Acclimation gets the animal into the water safely — it still needs to spend time in isolation first: why-you-need-a-quarantine-tank.
- Pouring bag/shipping water directly into the display or QT tank
- Float-and-dump only — that equalizes temperature, not salinity or pH
- Rushing an invertebrate through a fish-speed drip rate
- Coral Reef Knowledge Base (internal) — Fish Health & Disease / Invertebrate Care
- Coral Reef Knowledge Base (internal) — Quality Marine facility tour (WWC)